1. Field of the Invention
This invention relates to in-line roller skate wheels and more particularly to a pre-pressurized pneumatic skate wheel of integral polyurethane construction having contour conforming tire support wall.
2. Description of the Prior Art
Roller skates and roller skate wheels have been known in the art. Typically, roller skates have incorporated four wheels in each skate. Early wheels were constructed of either wood or metal depending on the intended use. Wood wheels were most often used for indoor roller rink skating while metal wheels were used for outdoor skating. Inflatable roller skate wheels, such as that disclosed in U.S. Pat. No. 988,533 to Zverina, provided a simple, durable and economic roller skate wheel. Zverina includes an inflatable tube encased in a conventional tire.
In the past, many skate wheels were constructed of rubber. The availability of polyurethane in skate wheel construction has enhanced the enjoyment and popularity of outdoor skating. Typically roller skates have been constructed with four wheels in a box-like configuration. Such skates, while functional, do not allow for the freedom of movement experienced by ice skaters. It was thus proposed to mount the roller skate wheels in a line along the skate frame to achieve mobility which closely mimicked the movement of an ice skate. Since that time, "in-line roller skates" have become one of the most popular recreational and physical fitness activities in the United States, and elsewhere. In-line skating has also developed into a highly sophisticated and technologically advancing commercial market.
The recreational skater often travels a variety of terrains ranging from concrete and wood to more bumpy and uneven surfaces such as asphalt which may exhibit bumps, pits and even wide cracks with vegetation growing therein. The main concern experienced by the recreational skater is to obtain a comfortable ride while skating socially, participating in physical fitness or even just a way to reach a destination. This skater requires a resilient wheel which is light weight and shock resistant. More experienced skaters, such as competitive skaters, employ in-line skates for sporting purposes such as hockey or road racing. Dancers typically prefer relatively hard tire bodies since some slippage is an acceptable compromise for the performance required. On the other hand, a hockey player would prefer a softer tire having excellent surface gripping characteristics. In the past, these various performance characteristics have been attained only by expensive painstaking manufacturing processes.
Polyurethane in-line skate wheels proposed in the past have typically been constructed by injection molding to form a hub surrounded by a tire body of solid urethane. It is desirable that such wheels provide a durable and relatively smooth ride over many types of terrains. Solid polyurethane bodies have been proposed. Such tire bodies are necessarily restricted in that the performance characteristics cannot be easily and inexpensively adjusted during the manufacturing process to accommodate the many different support surfaces and loads emanated by a skate employed in a demanding sport such as, for instance, hockey. Unlike a traditional quad or box-style roller skate, in-line skates are designed to withstand a variety of different side loads due to the inclination of the skate along its horizontal axis when turning, as well as high intensity shock loads from quick stops, bumps and other road hazards. Thus the designers of in-line skate wheels have an intensely difficult task when faced with such diverse performance requirements.
It has been proposed to construct an in-line skate wheel with a nylon hub having an annular gridwork defining axially through passages for receiving cross segments of urethane embodied in a tire body. A wheel of this type is shown in U.S. Pat. No. 5,028,058 to Olson. Wheels of this type, while satisfactory for their intended purposes, do not typically exhibit the durability and performance characteristics important to aggressive athletic roller skating activities, such as roller hockey and the like.
Other efforts to improve polyurethane wheels have led to the proposal that polyurethane be injected into a mold around a hard polyurethane hub having an annular grid work for interlocking of the resultant tire body with the hub to create a solid tire body. A device of this type is shown in U.S. Pat. No. 5,312,844 to Gonsior. Wheels of this type, while being acceptable for recreational skating activity, are relatively expensive to manufacture do not provide a tire periphery which will readily conform to irregular underlying surfaces or satisfactorily grip the underlying surface on sharp fast turns and the like.
Other efforts in polyurethane wheel design has led to the proposal of a hard polyurethane hub formed with a radially projecting annular ring configured with transverse through bores for flow of a liquid thermoplastic polyurethane tire material therethrough for mechanical interlocking thereof. A wheel of this type is shown in U.S. Pat. No. 5,567,019 to Raza. Wheels of this type, while satisfactory for recreational skating, are relatively expensive to manufacture and exhibit a relatively hard peripheral surface which provides for only limited cushioning and flexibility to accommodate irregular terrain and flexure to exhibit a relatively large foot print upon tight high speed turns for positive gripping of the underlying terrain.
In recognition of the desirability of an in-line skate wheel which combines the resiliency and performance of a polyurethane wheel with the enhanced grip, durability and shock absorption properties associated with hollow body wheel construction and which can be casted from thermoplastic polyurethane, applicants propose a solution in U.S. Pat. No. 5,630,891, assigned to the assignee of the instant application. That patent discloses an in-line skate wheel with an adjustable bladder encapsulated in a thermoplastic polyurethane wheel body. Pressure in the bladder is adjustable through the use of a valve system. Such a wheel allows the skater to adjust wheel performance to match his or her needs for the particular skating maneuver to be undertaken. Since the skater has multiple performance options available without purchasing multiple wheels and without having to manually change the skate wheels, such a wheel is versatile, cost effective and convenient. While having important commercial applications, it is recognized that such an adjustable pneumatic in-line skate wheel requires the skater to manipulate the wheel each time skate conditions change and the wheel itself is relatively costly to manufacture.
Another form of in-line skate wheel with similar urethane and pneumatic benefits can be found in our U.S. patent application Ser. No. 08/595,844 filed Feb. 2, 1996 now U.S. Pat. No 5,641,365, also assigned to the assignee of the instant application. In that application, we show a pre-pressurized pneumatic in-line skate wheel of integral construction and consisting of an annular bladder and a plurality of radially projecting bladder rods encapsulated in a thermoplastic polyurethane body. Such an invention is relatively cost effective to manufacture but employs a relatively elaborate bladder and valve construction.
In other areas of the art, such as in the construction of variable pressure athletic shoes, it has been known to provide elastomeric bladders configured with multiple discrete chamber or open cell elastomeric foam having inlet and outlet valves. Devices of this type are shown in U.S. Pat. Nos. 4,183,156 and 4,287,250 to Rudy and U.S. Pat. No. 5,144,708 to Pekar. However, such bladders have not been generally adapted to or employed in skate wheel construction.
Thus, there exists a need for a skate wheel which can be inexpensively casted from thermoset polyurethane by a method which allows for convenience adjustment of the tire body to exhibit different operating characteristics without the necessity of making entirely new molds or involving an expensive development procedure to develop new or different thermoplastic urethane. It has been discovered that soft polyurethane exhibits desirable characteristics for in-line skate wheels in that the outer peripheral tread surface tends to flex and compress in response to forces associated with rolling contact under load involving irregular support surfaces. However, solid thermoplastic polyurethane tire bodies suffer the shortcoming that they consume a substantial quantity of polyurethane and that the force absorption characteristics are not ideal. The performance factors with which an in-line skater is concerned for when skating over concrete, asphalt or a composition, are speed, grip, durability and shock absorption. While all four factors are important for active sports such as hockey, grip is critical to preventing slippage and minimizing abrasion and wear.
As can be seen, there remains a need for an in-line skate wheel which combines the benefits of the shock absorptive properties found in pneumatics with the resiliency of polyurethane, but in a manner that is easier and more cost effective to manufacture.